An electronic device may include a filter that selects signals of particular frequencies. For example, a high-pass filter may receive an input signal having high frequencies and low frequencies and may generate an output signal having fewer low frequencies than the input signal. As another example, a low-pass filter may receive an input signal having high frequencies and low frequencies and may generate an output signal having fewer high frequencies than the input signal. Another example of a filter is a bandpass filter.
A bandpass filter may select signals of a particular frequency band. For example, a wireless communication protocol may specify that radio frequency (RF) messages are to be sent using a particular frequency band. A receiver may process the messages using a bandpass filter to reduce signal components (e.g., noise or interference) outside the particular frequency band.
In some devices, a frequency band associated with a bandpass filter may be adjustable. For example, an active bandpass filter may be adjustable to select the frequency band. In some designs, components used to adjust the frequency band may be large, expensive, or associated with high power consumption. Reducing a size or number of the components may reduce effectiveness of adjustment of the frequency band. Further, the components may be associated with instability in some circumstances, such as if a number of circuit loops causes unstable circuit behavior (e.g., oscillations) during operation of the active bandpass circuit.